Electric signaling system



@et 6, 1936., s, 'R DURAND 2,056,423

ELECTRIC SIGNALING SYSTEM n Filed Oct. 4, 1934 45T-45T 5/ sa 53 PatentedOct. 6, 1936 UNITED STATES- rA-TENT OFFICE Claims.

This invention relates in general to signaling systems, andmoreespeciallyl to systems for transmitting signals by meansv ofelectromagnetic Waves. v

The invention is especially applicable to high power radio telegraph andother similar transmitting systems in which' the usual commercial lowfrequency alternating current is converted into direct currentofsubstantially constant voltage by electric valves ofl the Fleming, orlother similar two electrode type,r and supplied thereby to otherelectric valves ofthe audion, or other similar grid controlled type,which operater to produce continuousoscillations of high frequency forthe production of electromagnetic waves.

In order to modulate the high frequency oscillations to pro'ducersignalsit has heretofore been the practice to interrupt the operation of thevalve generating the high frequency oscillations by varying theexcitationk ofthe grid electrode thereof, or, as an alternative, tointerrupt the supply of the direct current to the oscillator, oramplifier, valve-'by means of an oil or other type of switch. As isknown, however, the operation by the first of thetwo methods hasfrequently resulted in unstable operation-of the oscillator, and thatthe frequent interruption of suchv currents, which often exceedsftykilowatts, by thev second of the two methods rapidly destroys thecontacts of the switch, necessitating frequent renewals and consequentinterruption of service.

It hasY now beendiscovered" that the difficulties heretofore experiencedin modulating the high frequency oscillationsmay be. entirely avoided bysubstituting for the valves of theA Fleming type three electrode valvesof the gaseous type, including such as the multi-anode mercuryv arcrectifier, and exciting the grid electrodes thereof in such manner as tocontrol, at will, the production, magnitude and duration of the highfrequency oscillations. l

The novel features which are believed to be characteristic oftheinvention are pointed out with particularity in the appended claims; the

invention itself, however, both as to its arrangement and method ofoperation, will best be understood by reference to the followingdescription taken in connection with the drawing in which:

Fig. 1 illustrates, in diagrammatic fashion, a transmitting systemwherein the invention has been embodied; and

Fig. 2 illustrates, in graphic fashion, the operating characteristics ofa preferred one of the (CL. Z50-17) types ofvalves suitable for use asthe amplier valve of` Fig. l.

Referring more particularly to the drawing and first to the system shownin Fig. 1, the numeral I designates a generator of radio frequencyoscillations as comprising a three electrode valve 2 of the high vacuumtype having an anode 3, a grid 6, and a cathode 4, which may be heatedto incandescence by any suitable source of current, such as the battery5 as shown. As shown the anode and cathode are connected by anoscillatory circuit containing the inductances I and 3, and a source ofcurrent Il, which may be a batteryy as shown, or may be either a director alternating current generator. The cathode 4 is also connectedexternally with the grid 6 through an inductance ID, inductively coupledwith the inductance 8f. With the anode and grid circuits connected asshown, as soon' as current starts to flow in the anode-cathodecircuit, acurrent is built up in the grid-cathode circuit which tends to ow intheA opposite direction and the grid will become negatively chargedrelative to the potential of the cathode. This cuts down the flow ofcurrent in the anode-cathode circuit and as the current decreases, thegrid loses'its negative charge and becomes positively charged relativeto the potential of the cathode. The changes are dependent on thenatural periods of the two circuits, they may take place with greatrapidity, and they may be readily varied to obtain any frequency desiredin the-inductance 'I-by varying the capacity of the adjustable condenserII.

In order that the stability of the oscillations produced in theinductance 'l may be maintained independentv of the constants of theload circuit herein, indicated as an antenna (which they would not beif, as for example, the inductance 'I was included directly in theantenna circuit), a second valve 2| is interposed between the generatorI and the work circuit, herein shown as comprising an antenna 3Dconnected through an inductance 25 with ground as at 26. This secondvalve has a lamentary cathode 22 which may beheated to incandescence byany suitable source of current, such as' the battery 2G, and isotherwise similar in construction to the valve 2, but is preferablyadapted to handle a greater amount of energy and as having the operatingcharacteristics of the 228--A type, indicated in Fig. 2 of the drawing.

The valve 2| is indicated as being Supplied with high voltage directcurrent from a valve lill, to be hereinafter described; and as beingcoupled with the generator I, and with the work circuit 30-25 by theconnection of the cathode 22 and grid 23 thereof with the inductance 1through a biasing battery 24 and an inductance I2 coupled with theinductance 1, and by the connection of the cathode 22 and anode 21 withthe inductance 25 through a direct current blocking condenser 28 and aninductance 29 coupled with the inductance 25. The latter circuit may,preferably, include an adjustable condenser 3| connected across theinductance 29 by which the Work circuit may be tuned to resonance at thefrequency of the oscillations produced in the inductance 1.

Numerous of the well known grid controlled gaseous type valves may beemployed for produc` ing .and supplying the high voltage direct currentto the valve 2|. rectifier is, however, particularly adaptable for thepurpose because of its ability to deliver greater power at a moreconstant voltage, and because of its infinite life. Accordingly, such avalve is illustrated as comprising a cathode 4| consisting of a pool ofmercury, a plurality of anodes 42, 43, 44, 45, 46 and 41, and aplurality of control electrodes 48, 49, 50,'5I, 52 and 53 severallyassociated with the anodes .and on which potentials are impressed tocontrol the moments at which the associated anodes will be operable to.start carrying current, as will be hereinafter described. It will beunderstood that such 'a rectifier is also provided with means forstriking an arc and for maintaining such arc as is well known in therectifying art and, therefore, notV shown or discussed herein.

The current from which the high voltage direct current is produced bythe valve action of the rectifier is indicated as being derived from alowl frequency polyphase alternating current circuit 54 through atransformer 55, having its delta connected primary winding 56 connectedwith the circuit 54 and the phase sections of its star connectedsecondary winding 51 severally connected with the anodes 42-41 of therectifier; and is supplied to the valve 2| through a conductor 58,connected with the cathode 22 of the valve 2| and with the star pointconnection of the winding 51, and through a conductor 59, connected withthe anode 21 of the valve 2| ,and with the cathode 4| of the rectifier40. A reactor 60 is also indicated as being included in seriesconnection with the conductor 59- and a condenser 6| connected acrossthe conductors 58 and 59 for smoothing out voltage ripples which might,otherwise, produce a ru'lng action on the signaling impulses produced inthe antenna circuit.

A preferred method for exciting the control electrodes 48-53 to controlthe rectifying action of the valve 40, and to thereby produce thesignals, consists in continuously impressing on each such electrode adirect current potential of variable magnitudes and of such sign as torender the control electrodes negative relative to the potential of thecathode 4|; and continually superimposing thereon alternating currentpotentials having a definite phase relation to the alternating currentpotentials impressed on the anodes 42--41 and of such magnitude as torender the control electrodes positive relative to the potential of thecathode 4| during the periods of signal production. Suchalternatingcurrent potentials are indicated in the drawing as being derived fromthe supply circuit 54 through .a control transformer 10, having itsdelta connected primary winding 1 |,connected with the supply circuitand the star connected phase sections of its secondary Winding 12severally connected with the control The multi-anode mercury arcelectrodes 48--53 through current limiting resistances 13; and thedirect current potentials as being derived from a direct currentgenerator 14, through a Voltage divider consisting of a resistor 15having a terminal thereof connected with the cathode 4| and a rheostat16 having the contact arm thereof connected with the star pointconnection of the winding 12. 'I'hus by varying the position of thecontact arm 11 on the rheostat 16 the moments at which the controlelectrodes are made positive, relative to the voltage of the cathode 4|,may be varied and the output voltage Epdc of the rectier regulated. Inaddition to regulating the effective voltage of the control electrodes48-53 by varying the effective resistance of the rheostat 16, and forproducing the signals, a relay 18 is provided having contacts 19 adaptedto short circuit the resistance 15 upon actuation thereof from a lowvoltage alternating current generator 80, through an insulatingtransformer 8| and the signaling key 82. Thus upon closure of thesignaling key 82 to produce a dot or dash element of a code message, therelay 18 operates to short circuit resistor 15 and thereby reduce thedirect current biasing voltage of the electrodes 48-53, which rendersthe .alternating current potential effective at an earlier moment in thevoltage cycle of the potential impressed on the anodes 42--41, withresultant increase of the output voltage Epdc to the valve 2|; and whenthe key 82 is released, during a spacing interval in the code, the relay18 instantly operates to remove the short circuit from about theresistance 15 thereby causing the direct current biasing voltage to beincreased with resultant lowering of the Epdcvoltage to the valve 2|. Bychoosing values for the direct current voltage of generator 14 and forthe resistance 15 it is readily possible to obtain a direct currentnegative biasing voltage of such value above the output voltage of thetransformer 10 as to cornpletely block the rectifying action of thevalve and thereby reduce the output voltage Epdc to Zero; or such valuesmay be chosen as Will merely reduce the 'direct current output voltageEpdc to a value which will prevent the radiation of radio frequencyenergy from the antenna circuit during code spacing intervals. Thislatter method is a feature of the invention and is of very materialimportance in keying radio transmitters as explained hereinafter inconnection with Fig. 2 of the drawing. Of course, the same results maybe obtained by varying the output voltage of the transformer 10 insteadof varying the direct current biasing voltage.

Fig. 2 of the drawing graphically indicatesy selected operating voltageand current values for a valve having the electrical characteristics ofthe 228-A type, which has been found to be particularly suitable for thevalve 2| in the practice of the present invention. As indicated in thedrawing this valve will, at the selected values, operate to deliverenergy to the antenna 3|] when the anode-cathode circuit thereof issupplied with current Io, from the valve 40, at voltages Epdc varyingfrom six thousand to ten thousand volts, against a negative grid biasingvoltage Egdc of one thousand volts when modulated bya radio frequencyvoltage Egrf, from the oscillator having a peak value of four hundredvolts. The instrumentalities of the oscillator are, there-V fore, soproportioned as to impress on the gridcathode circuit of the valveV 2|radio frequency voltages Egrf having a peak value of four hundred volts,and the voltage of the generator 14 and the resistor 15 are soproportioned that, during closed circuit periods of the key 82, toproduce dot and dash signaling elements of a code message, current Io issupplied to the valve 2i from the valve 40 at voltage Epdc of tenthousand volts and converted, by the action of the grid-cathode circuitI2, 22, 23, into'oscillations, corresponding in frequency to theoscillations produced in the Aoscillator l, and supplied, over theanode-cathode circuit 21--22, 29 and 28, to the antenna. circuit 25, 30,at a voltage as determined by the transformation ratio of theinductively coupled coils 25, 29. Between each such dot and dash impulsethe key is restored to its open circuit position which results in thevoltage Epdc being reduced to six thousand volts, atwhich point thecurrent I0 is reduced to zero by the biasing action of the Egdc voltage,and the valve 2l cuts off. The valve 40 then supplies only such directcurrent as is necessary to maintain the condenser 6| in its thenpartially charged condition. It is, therefore,

apparent that by the simple process of reducing the output voltage ofthe valve 40 from ten thousand volts to six thousand volts (a reductionof only forty percent) keying of the radio transmitter is accomplished.

Although but a single embodiment of the invention has been illustratedand described, it will be apparent to those skilled in the art thatvarious changes and modifications may be made therein to meet differentconditions encountered in its use without departing from the spirit ofthe invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a signal transmitting system, a source of alternating current,means comprising a multianode electric valve of the vapor arcing typehaving connections with said source and operable to convertcurrentsupplied therefrom into direct current by Way of arcs whensequentially established between said anodes and the cathode thereof,means supplied with said direct current operable to convert the sameinto electromagnetic waves, and means for controlling the creation andduration of said waves in accordance with signals to be transmittedcomprising in combination control electrodes severally associated withsaid anodes, means for exciting said control electrodes in such sense asto permit the establishment of said arcs at predetermined momentsrelative to the voltage frequency of said source of alternating current,and means operable in accordance with signals to be transmitted forvarying said excitation in such sense as to vary the moments ofestablishment of said arcs relative to the voltage frequency of saidsource of alternating current.

2. In a signal transmitting system, a source of alternating current,means comprising a multianode electric valve of the vapor arcing typehaving connections with said source and operable to convert currentsupplied therefrom into direct current by way of arcs when sequentiallyestablished between the said anodes and the cathode thereof, meanscomprising an electric valve having an anode-cathode circuit suppliedwith said direct current operable to convert the same intoelectromagnetic waves, means comprising a grid cathode circuit of thesecond said valve and an oscillator coupled therewith for determiningand controlling the frequency of said waves, and means for controllingthe creation and duration of said waves in accordance with signals to betransmitted comprising in combination control electrodes severallyassociated with said anodes of the `rst said valve, means forsequentially 'exciting said control electrodes in such sense inaccordance with signals to be transmitted for varying the saidexcitation in such sense as to 'vary the moments of establishment ofsaid arcs relative tothe voltage frequency of said source 4ofalternating current.

3. Ina signal transmitting system, a source of alternating current,means comprising a multianode electric valve of the vapor arcing typehaving connections with said source and arranged to convert currentsupplied therefrom into direct current at voltages above and below apredetermined voltage value by way of arcs when sequentially establishedbetween the said anodes and the cathode thereof, means comprising anelectric valve having an anode-cathode circuit supplied with said directcurrent and operable at the voltage thereof above said predeterminedvalue to convert the same into electromagnetic waves, means comprising agrid cathode circuit of the second said valve and a variable frequencyoscillator coupled therewith for regulating the frequency of said waves,and means for controlling the creation and duration of said waves inaccordance with signals to be transmitted comprising in combinationcontrol electrodes severally associated with the anodes of the firstsaid valve, means comprising a source of alternating current and asource of direct current connected with said control electrodes andimpressing voltage impulses thereon of such sign and magnitude andduring such recurring periods as to permit the establishment of saidarcs at such moments relative to the voltage frequency of the first saidsource of alternating current as to produce the direct current therefromat a voltage not to exceed said predetermined value, and meanscomprising a signaling key operable in accordance with signals to betransmitted for varying the potential of said impulses in such sense asto permit the establishment of said arcs at such moments relative to thevoltage frequency of the first said source of alternating current as toproduce therefrom the direct current at a voltage above the saidpredetermined value.

4. The combination with an electromagnetic wave transmitting systemcomprising an antenna system, an oscillating circuit coupled with saidantenna system and arranged to create electrical oscillations therein,and means for energizing said circuit comprising a source of alternatingcurrent, and an electric valve having anodes and a cathode connectedwith said circuit and with said source and arranged to convert currentsupplied from said source into direct current and the supply thereof tosaid circuit at voltages above and below a predetermined value, of meansfor controlling the creation and duration of said oscillations inaccordance with signals to be transmitted comprising control electrodesseverally associated with said anodes, a source of alternating currentconnected with said control electrodes and continually impressingpotential impulses thereon during such moments as to permit saidconverting operation of said valve, a source of direct currentcontinuously connected with said control electrodes and impressingthereon potential of such sign and magnitude as to modulate saidimpulses in such sense as to cause the production of the first saiddirect current at voltages below said predetermined Value, and meansoperable in accordance with signals to be transmitted for modulatingsaid impulses in such sense as to cause the production of the rst saiddirect current at voltages above said predetermined value. Y 5. In asystem of the character described, the combination with means forcreating electrical oscillations to produce signals, and means forenergizing the same comprising a source of alternating current and anelectric current converting device having electrodes connected With therst said means and with said source and arranged to convert currentsupplied from said source into direct current and to supply said directcurrent to the first said means, of means for controlling the creationand duration of said oscillations in accordance with signals to betransmitted comprising a control electrode associated with the rst saidelectrodes, means for continually impressing voltage impulses on saidcontrol electrode of such sign and magnitude and during such momentsrelative to the voltage frequency of said source of alternating currentas to cause the production of said direct current at a Voltage ofpredetermined value, and means operable in accordance with signals to beproduced for modulating said impulses in such sense as to cause theproduction of said direct current at a voltage above said predeterminedvalue.

- SAMUEL R. DURAND.

